The equilibrium free surface of a liquid in a partly filled circular cylinder under the action of surface and gravitational forces is determined by the static contact-angle and liquid volume and may be expressed as a function of the bond number Bo. A sudden step reduction in gravity causes a reorientation of the free surface due to the decrease of hydrostatic pressure and the dominating capillary forces. The resulting dynamic wetting process, the displacement of one fluid by another immiscible fluid on a solid surface, is of major interest to investigate the hydrodynamics near moving contact lines.